1. Field Of The Invention
This invention relates to a machine for preparing an infusion and, in particular but not exclusively, for preparing coffee.
More particularly, the invention relates to an infusion preparation machine that comprises an infusion chamber that is designed to receive a product to be infused and that is delimited by a lower vat and a so-called upper tamping head that move relative to one another, and a supply of pressurized hot water to the infusion chamber, whereby said tamping head comprises an internal tube that has an inlet that communicates with the infusion chamber and that makes possible the passage of the infusion through the tamping head in an upward direction toward a distribution outlet, and means that are located in said tube close to its inlet and suitable for forming foam in the infusion during its passage through the tamping head and for preventing the infusion from returning into said infusion chamber.
2. Description Of The Related Art
Such a machine is known from the document DE-U-20 2004 018 776, which relates to an espresso-type coffeemaker that comprises foam-forming means arranged in a vertical internal tube of the tamping head. These means consist of a valve that comprises a seat that is formed in the wall of the internal tube, a ball with a diameter that is suitable for resting in a sealed manner on the seat, and an open coil spring that is combined with a stop and pushes the ball against the seat. As indicated in this document, these means that form a valve make possible the formation of foam in the coffee. They also keep the coffee that is located above the ball from returning into the chamber after the percolation operation because of the spring pushing the ball against the seat.
These means that form a valve, however, use several parts that are expensive and difficult to install and that require a precise machining in the internal tube of the tamping head to form the seat against which the ball can rest in a sealed manner. This increases, of course, the production cost of the coffeemaker, primarily when it is desired to produce the latter on a large scale by reducing the production stages as much as possible. The effectiveness of these means that form a valve can also decrease after a large number of operating cycles if coffee deposits are formed at the level of the moving parts, in particular between the ball and its seat.